Tracing all the way back to apporx 3.5 billion years ago, single celled organisms began appearing, how those came is uncertain. We've created organic molecules by sending an electric shock (e.g. lightning) into water containing the same elements that were in earth's primitive oceans. It's a very plausible beginning to life on earth.
Now...if you want to go all the way back to the creation of the universe (i.e. the Big Bang 15 billion years ago) then I'm not sure what started the chain reaction of events that led to the laws of the universe (i.e. gravity) which drive the evolution of stars, planets, and ultimately elements that bind together and work together (e.g. life). If you want to believe in some intelligent force that started it all and let the laws of the universe run their course, then that is fine. I cannot argue for or against it. Nobody knows. But, for me, to say..."we don't know, so therefore it is God and we must worship him"...seems irrational. Instead of accepting the unknown as a god, we should strive to understand, and make the unknown, known.
What I do know for certain, is that there is no God that listens to our thoughts, punishes us for not worshipping him, follows everyones every move, loves us and hates us in the same moment, affects all life on earth, impregnated a woman with his son, etc, etc. Looking at all of the evidence, but most importantly, looking at the time scale (15 billion years) and the size of the universe, puts human life into perspective and lets us know that we are just a blink of an eye in the grand scheme of things and that there is no god that watches us or cares for us. We are on our own.
The Cosmic Calender. I hope this helps put humans into perspective.
quality post man.